Cabletron Systems 9H423-28 - Manual (Page 27)

3-3
Operation
SmartSwitch ASIC
The SmartSwitch ASIC is a hardware-based switch design that is the key building
block of the SmartSwitch 9000 hub. The SmartSwitch ASIC makes all filtering/
forwarding decisions in custom hardware as opposed to software, as in
traditional bridges. This custom hardware enables the SmartSwitch ASIC to
process over 750K frames per second. The SmartSwitch ASIC is designed to
support up to 64 ports shared between the host processor, the INB backplane, and
LAN/WAN interfaces on the front panel of SmartSwitch 9000 modules. The
SmartSwitch ASIC can operate in two modes: as a traditional switch
or as a
SecureFast Switch (SFS).
Traditional Switch
When operating as a traditional switch, the SmartSwitch ASIC makes filtering/
forwarding decisions based on Destination Address (DA), with standard IEEE
802.1d learning.
VLAN
Modules within a MMAC chassis utilize connection-oriented SecureFast Switches
(SFS) to create Virtual LANs, or VLANs.
A VLAN is a local area network of endpoints having full connectivity (sharing
broadcast, multicast, and unicast packets) independent of any particular physical
or geographical location. In other words, endpoints that share a virtual LAN
appear to be on a single LAN segment regardless of their actual location. Changes
to VLANs, (e.g., moving nodes) are accomplished via software, reducing network
management time and expense.
VLANs extend direct communication between users beyond the constraints of a
physical LAN segment by allowing the establishment of VLANs that encompass
users on multiple physical LAN segments. This permits endpoints to be
administratively grouped. For example, in Figure 3-2, the users on LANs A and B
belong to the Finance group, however, they are physically removed from each
other and as such cannot communicate directly. The VLAN solution places both
LAN segments on the same VLAN; all endpoints appear and act as if they are on
the same physical LAN.
Most VLAN implementations require a router for Inter-VLAN communication;
Cabletron’s SecureFast VLAN operational model does not. Inter-VLAN
communication is accomplished via multi-layer switches or optional traditional
router.